[BluffTHIS!]

Well beset, like I said too, I have never seen anything in a certain hand. But shared card knowledge could allow a couple players to know when you or they might be drawing better or thinner on a draw, or that a 3rd player is unlikely to have the hand represented on the river thus allowing one of them to make a "miraculous" call.

I've played with colluders in limit games in B&M cardrooms, and they really don't bother me there since there are actually ways to exploit that, and since a good cardroom manager will be willing to have a 3rd player's hand exposed from the muck when he didn't call the last bet in order to prove what is going on. But in big bet games online it's just not worth the risk if there is even a smaller possibility.